Background for a plug-in system as referred to herein is described in EP 0 005 865 B1, for example, but also in a number of later publications, such as EP 0 913 618 A1. In this connection, the screw-in part, which can also be referred to as a cap screw, is inserted with its externally threaded portion into a threaded bore of a base part or housing part (for example of a pressure unit). The threaded bore is part of a special “shaped bore”, on the one hand a radial step surface, which together with the screw-in part, or rather its end side, forms an annular chamber for receiving a holding ring element, being formed inside this shaped bore following the internal thread. The holding ring element serves for the positive locking of a plug part to be plugged into the through-opening of the screw-in part. The plug part is also removable by unscrewing the screw-in part together with the holding ring element. On the other hand, the shaped bore has on the mouth side a widening, which, together with the flange-like actuating shoulder (external hexagon) and the adjacent receiving groove of the screw-in part, forms a seal chamber for enclosed, compressed accommodation of a sealing ring. Moreover, the special shaped bore is designed in such a way with regard to its length, or rather depth, that on the one hand the screw-in part can be screwed in completely and tightened with the necessary torque and on the other hand the plug part can also be plugged completely into or through into its locked plugged-in position without colliding with the step surface in the shaped bore.
There are now applications in practice where such a plug-in system is to be inserted into other threaded bores, for example into a “standard bore” according to DIN 3852 (Part 1, Form Y). On the one hand, such standard bores have a surrounding surface directly adjacent on the mouth side without a seal widening (without chamber contour) and, on the other hand, they are as a general rule not designed deep enough. Use of the plug-in system described has therefore previously necessitated special adapters with, on one side a screw-in piece for the standard bore, and on the other side a lengthened portion with the shaped bore described above. On the connection side, toward the standard bore, such adapters have an axial receiving chamber for a (second) sealing ring in such a way that this sealing ring is enclosed when axial bearing contact is made with the surrounding surface of the standard bore. However, such adapters are expensive and lead to a disadvantageously large overall length of the arrangement as a whole.
The object of the present invention is to provide a simple and cost-effective possibility for equipping any “standard bores” as well with a plug-in system of the type described without in so doing bringing about an appreciable increase in overall length.
According to the invention, this is achieved by a novel adapter intermediate ring according to claim 1. Advantageous development features are contained in the subclaims. The intermediate ring according to the invention, which can be fitted directly coaxially onto the externally threaded portion of the screw-in part, consists of two axially opposite annular portions. The first annular portion having, on the side facing the actuating shoulder, a first seat, which, together with the receiving groove and the actuating shoulder, forms a first seal chamber for the first sealing ring located in the receiving groove. The second, directly adjacent annular portion has a second seat for a second sealing ring in such a way that, when the screw-in part is screwed into a threaded bore (standard bore) having a surrounding surface adjacent on the mouth side, a second seal chamber for the second sealing ring is formed between the second seat, the surrounding surface and the externally threaded portion. On the one hand, in the region of the first annular portion, the intermediate ring according to the invention has on the inside for all practical purposes the sealing ring chamber contour of the special shaped bore, as the sealing ring seat corresponds essentially to the widening of the shaped bore. On the other hand, the second annular portion is also designed for optimum enclosure of a second sealing ring, in fact, advantageously, in interaction with any standard bore as well, as the seat of the second annular portion corresponds for all practical purposes to the sealing ring chamber contour of the seal receiving chamber of known adapters.
According to the invention, the intermediate ring also acts as a distance ring at the same time, as it has an axial length, or rather thickness, dimensioned according to the threaded bore concerned in such a way that both on the one hand the screw-in part—if appropriate together with additional parts mounted thereon, such as in particular with a plug holding element (holding ring element)—can be screwed in completely to the requisite compression of the first sealing ring and on the other hand an associated plug part can also be plugged completely into or rather through the through-opening of the screw-in part into a correct plugged-in position. In this connection, however, the length/thickness of the intermediate ring should also be limited approximately to an adequate minimum value in such a way that the screw-in part is still located with sufficient stress-bearing thread turns, for example with at least three complete thread turns, inside the threaded bore.
Additional, very long adapters are rendered unnecessary by the intermediate ring according to the invention. Using the simply and rapidly fitted intermediate ring, the screw-in part of the plug-in system can advantageously be inserted directly into, for all practical purposes, any threaded bores. As a result, the overall length of the arrangement increases only slightly by merely the length, or rather thickness, of the intermediate ring. The intermediate ring according to the invention is moreover very much more cost-effective in comparison with known, large-volume adapters, because, with a much lower material requirement, it can also be manufactured more simply and more rapidly, in particular as a simple turned part made of brass, for example.